core: prevent endless region processing (#340)

jadx-core/src/main/java/jadx/core/dex/instructions/IfNode.java

 package jadx.core.dex.instructions;
 
+import java.util.List;
+
 import com.android.dx.io.instructions.DecodedInstruction;
 
 import jadx.core.dex.instructions.args.ArgType;
@@ -57,11 +59,12 @@ public class IfNode extends GotoNode {
 
 	@Override
 	public void initBlocks(BlockNode curBlock) {
-		thenBlock = getBlockByOffset(target, curBlock.getSuccessors());
-		if (curBlock.getSuccessors().size() == 1) {
+		List<BlockNode> successors = curBlock.getSuccessors();
+		thenBlock = getBlockByOffset(target, successors);
+		if (successors.size() == 1) {
 			elseBlock = thenBlock;
 		} else {
-			elseBlock = selectOther(thenBlock, curBlock.getSuccessors());
+			elseBlock = selectOther(thenBlock, successors);
 		}
 	}
 

jadx-core/src/main/java/jadx/core/dex/visitors/regions/IfMakerHelper.java

@@ -2,6 +2,7 @@ package jadx.core.dex.visitors.regions;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 
 import org.slf4j.Logger;
@@ -52,6 +53,12 @@ public class IfMakerHelper {
 		BlockNode thenBlock = info.getThenBlock();
 		BlockNode elseBlock = info.getElseBlock();
 
+		if (Objects.equals(thenBlock, elseBlock)) {
+			IfInfo ifInfo = new IfInfo(info, null, null);
+			ifInfo.setOutBlock(thenBlock);
+			return ifInfo;
+		}
+
 		// select 'then', 'else' and 'exit' blocks
 		if (thenBlock.contains(AFlag.RETURN) && elseBlock.contains(AFlag.RETURN)) {
 			info.setOutBlock(null);

jadx-core/src/main/java/jadx/core/dex/visitors/regions/RegionMaker.java

@@ -60,21 +60,26 @@ public class RegionMaker {
 
 	private final MethodNode mth;
 	private int regionsCount;
-	private Region[] regionByBlock;
+	private BitSet processedBlocks;
 
 	public RegionMaker(MethodNode mth) {
 		this.mth = mth;
-		this.regionByBlock = new Region[mth.getBasicBlocks().size()];
+		this.processedBlocks = new BitSet(mth.getBasicBlocks().size());
 	}
 
 	public Region makeRegion(BlockNode startBlock, RegionStack stack) {
+		Region r = new Region(stack.peekRegion());
+		if (startBlock == null) {
+			return r;
+		}
+
 		int startBlockId = startBlock.getId();
-		Region region = regionByBlock[startBlockId];
-		if (region != null) {
-			return region;
+		if (processedBlocks.get(startBlockId)) {
+			mth.addWarn("Removed duplicated region for block: " + startBlock + " " + startBlock.getAttributesString());
+			return r;
 		}
+		processedBlocks.set(startBlockId);
 
-		Region r = new Region(stack.peekRegion());
 		BlockNode next = startBlock;
 		while (next != null) {
 			next = traverse(r, next, stack);
@@ -83,7 +88,6 @@ public class RegionMaker {
 				throw new JadxRuntimeException("Regions count limit reached");
 			}
 		}
-		regionByBlock[startBlockId] = r;
 		return r;
 	}
 
@@ -201,6 +205,7 @@ public class RegionMaker {
 			loopStart.remove(AType.LOOP);
 			loop.getEnd().add(AFlag.SKIP);
 			stack.addExit(loop.getEnd());
+			processedBlocks.clear(loopStart.getId());
 			Region body = makeRegion(loopStart, stack);
 			loopRegion.setBody(body);
 			loopStart.addAttr(AType.LOOP, loop);
@@ -296,6 +301,7 @@ public class RegionMaker {
 		curRegion.getSubBlocks().add(loopRegion);
 
 		loopStart.remove(AType.LOOP);
+		processedBlocks.clear(loopStart.getId());
 		stack.push(loopRegion);
 
 		BlockNode out = null;

jadx-core/src/test/java/jadx/tests/integration/TestWrongCode.java

@@ -5,6 +5,7 @@ import org.junit.Test;
 import jadx.core.dex.nodes.ClassNode;
 import jadx.tests.api.IntegrationTest;
 
+import static jadx.tests.api.utils.JadxMatchers.containsLines;
 import static jadx.tests.api.utils.JadxMatchers.containsOne;
 import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.CoreMatchers.not;
@@ -18,10 +19,8 @@ public class TestWrongCode extends IntegrationTest {
 			return a.length;
 		}
 
-		@SuppressWarnings("empty")
 		private int test2(int a) {
 			if (a == 0) {
-				;
 			}
 			return a;
 		}
@@ -36,7 +35,11 @@ public class TestWrongCode extends IntegrationTest {
 		assertThat(code, containsOne("int[] a = null;"));
 		assertThat(code, containsOne("return a.length;"));
 
-		assertThat(code, containsString("return a == 0 ? a : a;"));
+		assertThat(code, containsLines(2,
+				"if (a == 0) {",
+				"}",
+				"return a;"
+		));
 	}
 
 	@Test